The need to conserve energy, concern for the environment, the minimization of battery footprints, and extension of battery life all converge to drive a need for microelectronic circuits, particularly in portable devices dependent upon battery power, to reduce power usage. For example, a common approach to control current consumption and protect power supplies such as batteries from potentially harmful load conditions is to implement a switch in series with the power supply. In operation, the switch is arranged to interrupt the connection to the power supply when the power rises or falls beyond a predetermined acceptable range, or when selectably switched through various methods. The trend in the art is to place more stringent efficiency requirements on such switching schemes. Ideally, power usage by such circuits would be zero power consumption in an “OFF” state, and minimal power consumption in an “ON” state.
In particular, battery powered applications create a pressing need for ultra-low current solutions in integrated circuits. For example, with lithium-ion and other common battery types, it is critical to monitor battery voltage. Too low or too high of a voltage placed on the battery can cause permanent electro-chemical changes to occur in the battery, causing damage or reducing the battery's charge capacity, diminishing its lifetime, or rendering it completely useless. Many circuits that are designed to monitor battery voltage are inescapably required to be powered by the very same battery that they monitor. For low-voltage detection and prevention (also known as undervoltage protection), this can be detrimental, since a constant current draw from the battery continues to decrease the battery voltage, placing the battery deeper into an undervoltage condition and exacerbating the potential for damage. Analogous problems can result from the occurrence of overvoltage conditions, undercurrent or overcurrent conditions, or underpower or overpower conditions. In each case, regardless of power supply type or battery type, circuit monitoring and switching reactive to monitored conditions would be beneficial for managing and protecting the power supply.
Due to these and other problems and potential problems, improved efficient voltage, current, and power level monitoring and switching circuits would be useful and advantageous in the arts.